1. Field of the Invention
This invention relates to a process for producing a copolymer of maleic anhydride and a C.sub.1 -C.sub.8 alkyl vinyl ether monomer, and, more particularly, to slurry polymerization of such monomers in a sterically hindered monoether solvent in the presence of a free radical initiator.
2. Description of the Prior Art
Copolymers of maleic anhydride and alkyl vinyl ethers are conveniently prepared by free radical precipitation polymerization of the monomer mixture in an aromatic hydrocarbon solvent, e.g., benzene, in the presence of a dispersion aid, such as a protective colloid. However, isolation of the copolymer as a powder requires an expensive process step, and it is difficult to remove the toxic aromatic hydrocarbon solvent from the copolymer.
Accordingly, it is an object of the present invention to provide an improved process for the production of copolymers of maleic anhydride and a C.sub.1 -C.sub.8 alkyl vinyl ether in the presence of a free radical polymerization initiator.
Another object of the invention is to prepare such copolymers by free radical slurry polymerization of the monomer solvent, wherein the copolymer is formed as a slurry in the reaction medium, and from which copolymer powders which are substantially benzene-free and which have low specific viscosities can be obtained easily.
A feature of the present invention is the use of a sterically hindered monoether as the reaction solvent in the process of slurry polymerization of monomers of maleic anhydride and an alkyl vinyl ether.
Another feature herein is the provision of copolymer powders of maleic anhydride and an alkyl vinyl ether which have a specific viscosity of less than about 2.1, and contain less than about 0.1% residual solvent, and is benzene-free.
These and other objects and features of the invention will be made apparent from the following more particular description of the invention.